Mann's co2detrend.f Calculation

If someone felt that it was necessary to detrend the bristlecone pine-based PC1 of Mann’s AD1000 network for CO2 fertilization, it’s doubtful that the initial instinct would be to coerce the data to a network of northern Canadian-Alaskan tree ring chronologies where the possibility of regional differences must surely be allowed for.

Inspection of Mann’s former FTP archive at the University of Virginia (which I fortunately archived before it was deleted) contains an interesting program entitled co2detrend.f (Mann’s main programs were not on the archive, but some programs were inadvertently left in the archive, including the program that calculated the tree ring network principal components – which was how we discovered Mann’s erroneous PC method.)

The program (which I’ve posted here) include the following interesting comments (in which Mann reports a correlation of 0.9 between the AD1000 PC1 and CO2:

The program itself is in Fortran, which is highly verbose for simple operations like calculating a mean or standard deviation, that’s for sure. Below I’ve shown what is more or less a transliteration of his program into R so that you can see what the calculation does in simpler terms.

He first reads in the AD1000 Mannomatic PC1 and CO2 levels (with the 1610-1995 mean subtracted). I’ve uploaded both the source files to CA so that the commands below are fully operational (up to the need to take care with what WordPress does to quotation marks.) (The short R-script is here in ASCII form.)

For the portion before 1610, I used the average CO2 value for the period 1610-1980 in the adjustment. Then plot. Here I’ve plotted the output from the co2detrend.f program against the “fixed” PC1 (which ties in to MBH99 Figure 1), both rescaled to match the scale of MBH99 Figure 1a.

For those of us who work the policy end of this AGW mess, Mr. McIntyre is a godsend. When the whole story is finally written about “climate change”, McIntyre and McKitrick will be the superstars that Al Gore only thinks he is. Keep doing what you’re doing. We are very close to bringing accountability and science back together.